A subspecies of the Black-crowned Night-Heron (‘Auku‘u; Nycticorax nycticorax hoactli) inhabits wetlands throughout the Hawaiian Islands. The global population of Black-crowned Night-Herons primarily forages at night, extending foraging hours during the breeding season. No studies have examined Black-crowned Night-Heron foraging activity in the Hawaiian Islands, but the population has been described as diurnal, based on anecdotal observations. The goal of our study was to compare foraging activity of the Black-crowned Night-Heron in Hawai‘i during the day and at night. Surveys were conducted during daytime and nighttime to compare the number of strikes for prey made by focal individuals. In a brackish marsh, the number of strikes per focal individual was similar between daytime and nighttime, and no individuals were observed striking during surveys in a freshwater marsh, although individuals were present and presumably foraging. Black-crowned Night-Herons in this study appeared to have a broader temporal niche, perhaps due to minimal competition from diurnal wading birds, energy needs during breeding, or abundance of prey due to seasonal conditions.

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